Dental panoramic imaging system

ABSTRACT

An imaging system for producing a panoramic radiograph of a patient&#39;s jaw for dental analysis includes an X-ray source ( 2 ) carried at one end of an arm ( 1 ) and detector means ( 7 ) at the other end. The front surface of the detector means ( 7 ) carries scintillator material ( 8 ) which substantially solely defines the area of the detector means at which the image information is captured. The secondary diaphragm or slot used in conventional panoramic X-ray imaging systems can thus be omitted, giving a less complicated system.

This invention relates to imaging systems and more particularly tosystems suitable for dental X-ray diagnosis where the system may be usedto produce panoramic radiographs of the jaw of a patient.

In conventional dental X-ray systems for producing panoramicradiographs, an X-ray source is directed at the patient and an imagerecorded on a moving X-ray film. A secondary diaphragm having a slot islocated in front of the X-ray film as an aperture to define the part ofthe film where the radiation-is incident. It has previously beenproposed to replace the moving X-ray film by a CCD sensor. In thissystem, a unit is used which is rotatable about a vertical axis andwhich carries an X-ray source at one end of an arm and a CCD sensor atthe other end of the arm located behind a secondary diaphragm. Thesecondary diaphragm includes an opening or secondary slot which acts asthe aperture.

According to a first aspect of the invention, there is provided animaging system for dental use comprising: a source of X-ray radiation;solid state detector means having a radiation sensitive region whichincludes an image area at which charge accumulates which isrepresentative of incident radiation, the extent of the image area beingdefined substantially solely at the detector means: means for moving thesource and detector means relative to a subject to be examined, in whichthe subject is arranged to be located between them and means forprocessing the output of the detector means to obtain a panoramic imageof the subject.

The inventor has realised that the secondary slot previously consideredto be an essential feature may be eliminated from the system withoutcausing image quality deterioration to such an extent that it is nolonger satisfactory and in certain cases that elimination of thesecondary slot may improve image quality.

The image area is defined substantially solely at the detector means andobviates the need for a secondary slot or opening in a diaphragm to beused to define the aperture area as required in the conventional movingX-ray film arrangement or the previously proposed CCD sensor systems.This produces a more simplified system compared to previously knownarrangements which is less bulky and allows for more precise control ofthe alignment and movement of the arrangement, improving reliability.Also, use of the invention facilitates assembly and eases designconstraints. In some situations a secondary slot may be responsible forgenerating scattered radiation which degrades the image. Elimination ofthe slot by employment of the invention can thus improve image quality.

In one advantageous embodiment of the invention, the detector meansincludes scintillator material carried on its surface for convertingX-ray radiation into radiation of another wavelength for detection bysaid detector means and the image area is defined at the detector meansby the extent of the scintillator material on the detector means. Thescintillator material which converts incident X-ray radiation into awavelength to which the detector means is responsive may be carrieddirectly by the surface of the detector means or on an intermediatelayer laid down on the detector means.

In another advantageous embodiment of the invention, the extent of theimage area is defined by the location of charge storage means at whichradiation is incident to cause the accumulation of charge. Thus, wherethe detector means is a CCD sensor array, the location of charge storagesites defines the image area. Scintillator material may be used on theCCD array in register with it to further define the image area extent orcould alternative extend beyond the charge storage sites in one or moredirections.

It may be advantageous in some embodiments in accordance with theinvention to include shielding material on the surface of detector meanssurround in the scintillator material to absorb stray X-ray radiation.Preferably the solid state detector means is a CCD array but other typesof sensor may be used.

According to a second aspect of the invention, an imaging system fordental use comprises a source of X-ray radiation; solid state detectionmeans having a radiation sensitive region which includes an image area:means for moving the source and detector means relative to a subject tobe examined, the subject being arranged to be located between them: andmeans for processing an output of the detector means to obtain apanoramic image of the subject, and wherein no secondary slot is locatedin front of the detector means.

According to a feature of the invention, there is provided solid statedetector means for use in an imaging system in accordance with theinvention.

Some ways in which the invention may be performed are now described byway of example with reference to the accompanying drawing in which:

FIG. 1 schematically illustrates a dental X-ray arrangement inaccordance with the invention; and

FIGS. 2 and 3 schematically show alternative detector means for thearrangement of FIG. 1.

With reference to FIG. 1, an X-ray system for producing radiographs of apatient's jaw includes an arm 1 carrying an X-ray source 2 at one endand a detector arrangement 3 at the other end. At the mid-point of thearm 1 a shaft 4 is vertically extensive and in use is located over thepatient's head and rotates as shown by the arrows about its longitudinalaxis. The X-ray source 2 is located within a housing 5 having a slot 6to define a beam of X-ray radiation and is adjusted in position so thatthe radiation is incident on the patient's jaw. After passing throughthe jaw the attenuated X-ray radiation is then incident at the detector3. The detector 3 includes a CCD sensor array 7 having a layer ofscintillator material 8 laid down on its surface at which the X-rayradiation is received. The scintillator material 8 is of a configurationwhich corresponds to the slot 6 in the housing 5 of the X-ray source andthe extent of the material 8 defines the image area. As the arm 1 isrotated about the axis X-X of the shaft 4, different regions of thepatient's jaw are irradiated and imaged by the CCD sensor array 7. Theimage information produced at the sensor array 7 is clocked out at anappropriate rate to produce the required panoramic image. This may bestored for later analysis and/or displayed on a VDU.

In another detector means, as shown in FIG. 2, shielding material 9 isarranged around scintillator material 10 to absorb any X-rays incidenton the CCD detector array 11 outside the scintillator material 10.

In another arrangement, as shown in FIG. 3, scintillator material 12covers an area larger than that defined by the slot in the X-ray housingand extends beyond the radiation sensitive region of the CCD detectorarray 13. In this embodiment the radiation sensitive region defines theimage area of the X-ray system.

What is claimed is:
 1. An imaging system for dental use comprising: asource of X-ray radiation; solid state detector means having a radiationsensitive region which includes an image area at which chargeaccumulates which is representative of incident radiation;- scintillatormaterial carried on the surface of said image area for converting X-rayradiation into radiation of a different wave length for detection bysaid detector means, there being no secondary diaphragm or slot servingas an aperture in said system to define said image area; means formoving said source and said detector means relative to a subject to beexamined, in which the subject is arranged to be located between them;and means for processing the output of said detector means to obtain apanoramic image of the subject.
 2. A system as claim 1 wherein saidimage area being defined at said detector means by the extent of saidscintillator material on the detector means.
 3. A system as claimed inclaim 1 wherein the extend of the image area is defined by the locationof charge storage means at which radiation is incident to cause theaccumulation of charge.
 4. A system as claimed in claim 1, wherein saidsolid state detector means is a CCD array.
 5. A system as claimed inclaim 1, wherein said image area is surrounded by shielding material forabsorbing X-ray radiation incident on said detector means outside saidimage area, said shielding material and said detector means beingcarried on a common mount.
 6. A system as claimed in claim 5 whereinsaid scintillator material and said shielding material lie insubstantially the same plane.
 7. A system as claimed in claim 1 whereinsaid X-ray source includes a diaphragm having a slot therein definingthe configuration of the X-ray beam which irradiates a subject andwherein said image area is of substantially the same dimensions as saidslot.
 8. Solid state detection means for use in an imaging system inaccordance with claim 1.